Anion-exchange polymers of vinylanisole



' Patented May 20, 1952 ANION-EXCHANGE POLYMERS F VINYLANISOLE Jesse C.H. Hwa, Philadelphia, Pa., assignor to Rohm & Haas Company,Philadelphia, Pa., a

corporation of Delaware No Drawing. Application May 12, 1951, Serial No.226,097

2 Claims. (Cl. 260-47) This invention relates to anion-exchange polymersand to their preparation and use. It relates to insoluble anion-exchangeresins of the weakly basic type which are proliferous polymers and whichare characterized by unusually large areas of surface, very high degreesof porosity, high adsorptive capacity, and very rapid rates ofadsorption. More specifically it relates to the preparation and use ofpolymers which have the chemical properties of weakly basicanion-exchangers and the physical properties of the socalled popcorn orproliferous polymers. As a result of this peculiar combination ofchemical and physical properties, these ion-exchange resins havedistinct advantages in some applications over the harder and denserweakly basic anion-exchangers employed heretofore. They are particularlysuitable for use in catalysis, in peptic ulcer therapy, and indecolorization of beet sugar syrups because of their high surface areasand their very rapid rate of adsorption of acids.

Other anion-exchange resins of the weakly basic type are well known andare marketed in large volumes for the deionization of aqueous fluids ingeneral. Such resins as are being currently used are described, forexample in U. S. Patent No. 2,356,15l-.and in C. H. McBurneys UnitedStates application Serial No. 759,309, filed July 5, 1947, and arecharacterized by being hard,

dense, infusible, insoluble, granular or spheroidal particles. As far asthe chemical properties of these known resins and the chemistry ofionexchange are concerned, the available products are very satisfactory.But the physical properties of these materialsparticularly their hard,dense, granular form-limits their utility in many instances where theirchemical properties would appear to make them ideally suited.

The products of this invention are all insoluble, proliferous or popcornpolymers. They are water-insoluble, proliferous polymers ofvinylanisole, to the aryl nuclei of which are attached amino groups. Theamino groups are attached to the aromatic nuclei by means of alkylenegroupspreferably by methylene groups. polymers are made, as will bedescribed in greater detail below, by haloalkylatingpreferablychlorome-thylatingan insoluble, proliferous polymer or copolymer ofvinylanisole and then reacting the haloalkylated, proliferous productwith a primary or secondary amine. As a result, the products areinsoluble, proliferous polymers which are. suitable for the removalv of.anions from. fluids and which comprise the reaction product of anamineand av haloalkylated, proliferou's copoly- These mer of a majorproportion of vinylanisole and a minor amount of a. polyolefiniccompound-- such as divinylbenzene, butadiene, or isoprenein which theolefinic linkages are in the acyclic portion of the molecule and are thereactive groups which enter into the proliferou copolymerizationreaction, said proliferous copolymer containing an average of 0.2 to 1.5haloalkyl groups per aromatic nucleus and the amine being either aprimary or a secondary amine.

The proliferous polymers of vinylanisole, from which the anion-exchangeresins of this invention are made, are themselves prepared mostconveniently by maintaining at a temperature from about C. to 100 C.andpreferably from. C. to C.a mixture of vinylanisole and an auxiliarypolyolefinic compound which is copolymerizable with the vinylanisole andin which the olefinic linkages are in the acyclic portion of themolecule and are the sole functional groups which take part in thecopolymerization reaction. It is suggested that the copolymerization becarried out in a closed system where the amount of oxygen is negligible.It is even better to conduct the copolymerization in an inert atmospherebecause oxygen exerts an inhibiting effect on the formation of theproliferous product. The addition of a small but catalytic amount of apreviously prepared proliferous polymer is also recommended since itserves as a seed from which the proliferous polymer grows rapidly.

Proliferouspolymers or copolymers' of vinylanisole are believed to benew, although other kinds of proliferous polymers have been known forsome time. Thus Kondakow (J. prakt. Chim. [.2'] 64, 109 (1901));Carothers- (J. A. C. S. 53, p. 4203 (1931)) Staudin-ger et a1.('Berichte 68, p. 1618 (1935)); Britton (U. S. Pat. No. 2,341,175 ofFebruary 8,. 1944) Kharasch et a1. (Ind. Eng. Chem. 39, p. 830 (1947))and others have described various popcorn or proliferous polymers fromother unsaturated, monomeric materials. Such popcorn polymers aredistinct kinds of polymers and theyhave a community of physicalproperties. They are opaque, they have a spongelike, porous structure,and. they are insoluble in the very solvents which dissolve thehomogeneous, thermoplastic polymers which are normally made from thesame monomers. In most cases they look very much like popcorn and havebeen variously described as sponge-like, cauliflowerlike, andcoral-like. They have extremely high molecular weightsandare apparentlycross-linked to. some. extent. In. addition, they are formed by an.auto-catalyzed polymerzation andthe' charmonomeric material at allstages of the poly- I merization and that polymerization progresses inrandom directions with the formation of a branched or clustered,expanded or popped product. That is, polymerization progresses byproliferation with the rapid and repeated production of new parts; andfor this reason the term proliferous polymer, which has been applied tothis kind of polymer and which is now synonymous with popcorn polymer,is particularly apt-and is truly descriptive.

This invention relates primarily to the preparation of proliferouspolymers of vinylanisole and to their conversion to anion-exchangeresins which retain the physical properties of the proliferouslypolymerized vinylanisole from which they are made. This is not to say,however, that the conventional, non-proliferous, clear, cross-linkedpolymers of vinylanisole cannot also be converted to anion-exchangeresins. They can be. But they do not give rise to resins with as largesurface areas, or as rapid rates of adsorption, or as high capacitiesper unit of weight as are obtained from the proliferous polymers.

As a matter of fact, some of the clear, non-.

proliferous polymer is frequently formed together with the proliferouspolymer; and while this can be separated, it does not have to be, sinceit reacts chemically like the proliferous polymer and its presencemerely dilutes, as it were, the advantages of the proliferous polymer.

In general, low temperatures favor the forma tion of proliferouspolymers whereas higher temperatures favor the formation of the clearpoly-z mers. For this reason it is preferred that the polymerization ofvinylanisole be carried out at temperatures from about 50 C. to 80 C. Inthis range the rate of (formation of the proliferous polymer is fastenough to be practical while the formation of the clear, non-proliferouspolymer is negligible-particularly in view of what was discussed above.At temperatures from 80 C. to 100 C. the proportion of clear polymerincreases at the expense of the proliferous product and above 100 C. theclear product forms to the complete exclusion of the proliferous resin.

A wide variety of polyolefinic compounds, as described above, definitelyassist in the formation of the popcorn polymers of vinylanisole. Theauxiliary compounds function as popping agents. Examples of some of thebest auxiliary agents include divinylbenzene, isoprene. butadiene,bimethallyl, biallyl, trivinylbenzene, dicyclopentadiene, and similarpolyolefinic hydrocarbons. Also effective are other unsaturatedcompounds such as dimethallyl ether and sulfide, vinyl allyl ether andthose unsaturated esters, such as diallyl maleate and 2-chloroallylcrotonate, which are disclosed in U. S. Patents Nos. 2,311,615 and2,341,175. The auxiliary compounds copolymerize with the vinylanisoleand consequently are present in the final copolymeric products.

The most satisfactory and suggested amounts of auxiliary compounds arefrom 2% to 30%,

based on the weight of this material and of the I vinylanisole. The useof larger amounts has been studied but there does not appear to be anyadvantage in exceeding 30 %-or even 20 particularly when theion-adsorbing capacity of the final product is considered. While all ofthe auxiliary compounds are alike in having a plurality ofnon-benzenoid, olefinic linkages or double bonds in their chemicalstructure, and in facilitating the popping of vinylanisole, it is alsotrue that these compounds differ in degree in regard to the effect theyhave on the density and porosity of the final copolymer. For example,divinylbenzene, which is recognized as a particularly fast and efficientcross-linking agent for vinyl compounds in general, aids very materiallyin the popping of vinylanisole, but it also gives rise to harder, lessporous popcorn polymers than do many of the other auxiliary agents suchas butadiene or isoprene. Consequently the amount, within the limits setforth above, of the auxiliary oopolymerizable compound which is employedis determined by the degree of porosity or extent of surface-area whichis desired in the final product.

The use of a seed to promote the proliferous polymerization is notnecessary but is most desirable. The material which is used as a seedcan have the same chemical composition as the proliferous polymer whichit is desired to make or it can have a different chemical composition. Aconvenient method involves adding a small amount of a previous batch ofproliferous polymer to subsequent mixtures of monomeric material whichare to be popped. Even the quantities of one batch which may adhere tothe equipment serve to seed subsequent batches. The word seed is usedherein in the accepted chemical sense and itself indicates that theamount required is very small and that the material is insoluble in thereaction mixture. As little as about 0.001%, on a weight basis, isadequate.

vinylanisole can be made to polymerize proliferously in bulk or insolution or whil suspended in an immiscible liquid medium. The advantageof carrying out the polymerization by the suspension technique is thatthe final product is obtained in the form of discrete particles whichadsorb ions unusually rapidly and which, although small, possess theadvantageous properties of popcorn polymers such as porosity, highsurface area, and rapid rates of adsorption.

It appears that free radicals, such as are provided by peroxidiccompounds, play a part in the formation of the opaque, proliferouspolymers, just as they do in the formation of clear, glasslike polymers.In proliferous polymerization, however, the amount of the peroxidiccompounds, such as benzoyl, lauroyl, stearoyl peroxides, tert.- butylhydroperoxide and the inorganic per-salts, which can be tolerated isrelatively very low and shall not exceed 0.5% on a weight basis becauselarge amounts of such compounds favor the formation of the clear,glass-like polymers at the expense of the opaque, proliferous polymers.In like manner, a steady and continuous source of oxygen is to beavoided. That is to say, oxygen should be eliminated and, although theamount of air which is normally present in a closed reaction vessel isnot too objectionable, it can be replaced to good advantage by an inertgas such as nitrogen. Thus, it is most desirable to conduct theproliferous polymerization in the substantially complete absence ofoxygen.

The proliferous polymers and copolymers of vinylanisole are firsthaloalkylated and then reacted with a primary or secondary amine. Thisstep of haloalkylating involves introducing into a proliferous polymer aplurality of bromoalkyl or, preferably, chloroalkyl groups-having thegeneral formula CnHZnX, in which n is an integer of value one to fourand X represents an atom of chlorine or bromine. While groups containingone tofour carbon atoms are embraced by this invention, it is preferredto employ those compounds in which chloromethyl groups, --CH2Cl-, areadded toth insoluble polymer, because the chloromethyl products are byfar the most reactive. The carbon atoms in the group -CnH2nX may" be ina straight or a branched chain.

The step of haloalkylating the insoluble copolymer may be carried out ina variety of ways. For example, the polymer may be reacted with amixture of an aldehyde and hydrochloric acid or a mixture of a dihalid'eand a Friedel-Crafts catalyst. Methods of chloroalkylating which may beused for introducing the CH2Cl group and which also serve as guides forintroducing C2H4X, --C3H6X, and.--C4HsX groups are described in OrganicReactions," vol. I, chapter 3, page 63 et'seq. ("John- Wiley & Sons,Inc., New York city, 1942) The extent of the haloalkylation reaction maybe conveniently determined by a halogen. analysis. It. isdesirable thatas many haloalkyl groups as possible be introduced into the insolublecopolymer because th number of such groups determines the number ofmolecules of the. amine which may be subsequently introduced into theresin molecule; and, of necessity, the number of molecules of amine thusintroduced determines the ultimate. capacity of the resin to adsorbanions. Although resins containing relatively few amino groups have somecapacity for adsorbing anions, it is necessary from a practicalstandpoint: to add a large. number of such groups in order to produce aresin of sufficiently high capacity as to be commercially attractive.And since, as stated, the number of molecules of amine which can reactis determined largely by the number of haloalkyl substituents in theresin molecule, it is important that the minimum number 01- suchsubstituent haloalkyl groups should be one for every fifteen anisolenuclei. The upper limit is reached when every available position in thearomatic nuclei is haloalkylated. Satisfactory resins of high capacitycan be made in which the number of haloalkyl groups, and hence thenumber of molecules of reacted amine which are introduced, is less thanthe theoretical maximum. Thus, very valuable resins are those made byaminatingcopolymers containing from three to six haloalkyl groups forevery four aromatic ani'sole nuclei.

The next step in the formation of the anionexchange resin istheamination of the haloalkylatedcopolymer with a primary and/or asecondary amine. This reaction is preferably carried out by adding theamine to the haloalkyl'ated polymer while the latter is suspended andagitated in a liquid which is a solvent for the amine. The mixturemay'be allowed to react atroom temperature or, preferably; at elevatedtemperatures, after which the resin, containing amino groups, is freedfrom the liquid.

It has been found to be advantageous to swell the haloalkylated polymerprior to its reaction with the amine. This swelling facilitates thesubsequent amination reaction and may be carried out by soaking thepolymer in a suitable liquid, the most common of which are aromatichydrocarbons such as benzene and toluene. Frequently, the volume of thepolymer will increase as much as 100%, although the amount of swell.-ing depends to a great extent upon the amount I of cross-linking whichhas taken place during-the preparation of the original polymer. Ingeneral, the amount of swelling is inversely proportional to the degreeof cross-linking.

The amines which are employed are used in the form of the free base. Theprime require-- ment is that they contain at least one aminonitrog'enatom to which is attached one or two reactive hydrogen atoms. The amineswhich are preferred in this application are those which are primary orsecondary and in which the amino group or groups are attached to ahydrocarbon group. Other amines may be used, however, including thosewherein the hydrocarbon group of the amine carries a substituent group.Suchamines may be exemplified by ethanolamine and diethanolamine. Forbest results, the amino compound should not contain substituent groupswhich are themselves reactive under the conditions employed in aminatingthe haloalkylated resin.

As stated, the preferred amines are those in which the amino-nitrogen.atom. is attached to one or two unsubstituted hydro-carbon groups.Primary and secondary amines are operable, as well asmixturesof the twotypes, and polyamines, including those having primary and secondaryamino groups such as polyalkylene polyamines. The. hydrocarbon portionof the amine may be aliphatic, aromatic, cycloaliphatic, araliphatic,and. alkaromatic. The following typify those amines which are allsuitable in this invention when used individually or in. mixtures withone another: Methylamine, dimethylamine, rL-butylamine, iso-butylamines,dibutylamines, aniline,

benzidine, 0-, m-, and p-toluidines, xylidines,.

alpha-- and. beta-naphthylamine, naphthalene diamines,v benzylamine,dibenzylamine, phenylene diam-inc, benzyl aniline, benzyl. ethylamine,methyl aniline, cyclohexylamina. dicyclohexylamine. diethylene triamine,triethylene tetrami'ne, tetraethylene pentamine,3,3-iminobispropylamine, and propylene diamine.

The following examples in which all parts are by weight are presented inorder that the preparation and properties of the products of this, in--vention may be thoroughly understood and recognized. The examples, whichare illustrative, are not to be taken, however, as: limiting thisinvention.

EXAMPLE 1 This servesto show how monomeric vinylanisole can be.conveniently converted into prolifercus or popcnrnpolymers- In each casea glass tube was partially filled with. the mixture of viny-l'ani'soleto be popped.' A small piece-a seed-of a previously prepared.proliferous copolymer of approximately v-inylanisole and 10% isoprenewasadded. The mixtures contained a major portion of vinylanisole and. a.minor portion of. a polyolefinic, auxiliary compound as a popping agentwhich was known to be copolymerizable with the vinylanisol'a. Nitrogenwas. bubbled through the mixture. in order to flush oxygen from the.tubes. and. thereafter the, tubes were sealed with foil-lined caps andwere placed in a constant-temperature water-bath. The kinds and amountsof the auxiliary popping agents which copolymerized proliferously withthe vinylanisole are listed below in Table I together with otherpertinent data. The percentages of the components of the mixture arebased on the total weight of the copolymerizable mixtures. An inductionperiod, as recorded, is that length of time during which no visiblechange takes place in the monomeric mixture and is followed by a periodof propagation during which the polymer is formed on the seed byproliferation. Ordinarily, the induction period is several times as longas the period of propagation.

The commercial divinylbenzeue contained approximately 44% divinylbenzeneand 56% ethylstyreue.

EXAMPLE 2 A proliferous copolymer of 90% vinylanisole and butadiene wachloromethylated as follows: 23.3 parts (equivalent to 0.15 mole ofpolymerized vinylanisole) of the copolymer (the first described inExample 1 above) was soaked in 370 parts of ethylene dichloride for onehour, during which time the polymer swelled markedly. To the mixturecontained in a 3-necked flask equipped with stirrer, thermometer, andreflux condenser was added 36 parts (0.45 mole) of chloromethyl ether,CH2C1OCH3, and this mixture was stirred at room temperature for one andone-half hours. Then 60 parts (0.45 mole) of anhydrous aluminum chloridewas added slowly while the mixture was maintained at a temperature of-30 C. by means of external cooling. The mixture was stirred andmaintained at room temperature overnight. Thereafter 600 parts of waterwas added and the resultant mixture was stirred for one hour. The resinwas filtered ofi and was thoroughly washed with water, after which itwas dried in an oven overnight at 65 C. Analysis showed that the productcontained 8.1% chlorine (corresponding to a product in which 81% of thearomatic nuclei were chloromethylated. Inspection revealed that thischloromethylated material was still in the form of a popcorn orproliferous polymer.

EXAMPLE 3 The chloromethylated proliferous product of Example 2 wasaminated as follows: in a 3- necked flask equipped with stirrer,thermometer, and reflux condenser were mixed eight parts of the dryproduct of Example 2 and 70 parts of toluene. The mixture was heated at80 C. for an hour during which the polymer swelled after which it wascooled to room temperature. Then 19.3 parts of diethylenetriamine wasadded and the mixture was heated to refluxing temperature and held therefor five hours. The reaction mixture, cooled to room temperature. wasnext filtered and the resinous product was washed thoroughly with waterand was then stripped 01' toluene and amine by steam-distillation. Thefinal product was separated and dried. When tested with a. solution ofhydrochloric acid it was found to have a capacity of 2.6mini-equivalents for each. gram of dry resin and had the same generalphysical structure as the original proliferous vinylanisole copolymerand the chloromethylated copolymer from which it was prepared.

The method described above was iollowed in the preparation of a widevariety of proliferous polymers having ion-exchange properties bychloromethylating the other proliferous vinylanisole polymers of Example1 above and then aminating the chloromethylated products with suchamines as dimethylamine, ethylamine, triethylenetetramine, andtetraethylenepentamine. All of the products retained the generalphysical properties of the popcorn vinylanisole copolymers from whichthey were made.

The products of this invention are all members of that class ofcompounds known as weakly basic anion-exchange resins. Thus, they doadsorb acids from fluids but are not capable of splitting neutral saltssuch as sodium chloride. For the latter purpose a strongly basicanionexchange resin is necessary such as the proliferous polymers ofvinylanisole which contain quaternary ammonium groups and which aredescribed in another of my applications, Serial No. 226,098, filed May12, 1951.

I claim:

1. As a new composition of matter, an opaque, infusible, proliierouspolymer which is capable of adsorbing acids from fluids and which comprises the reaction product of an amine from the class consisting ofprimary and secondary amines and a haloalkylated proliferous polymercontaining at least 70% proliferously polymerized vinylanisole to thearomatic nuclei of which are attached substituent haloalkyl groups ofthe formula in which n is an integer of value one to four and X is anatom of a halogen from the class consisting of chlorine and bromine, thenumber of said substituent groups being at least one for every 15aromatic nuclei in said polymer.

2. As a new composition of matter, an opaque. infusible, proliferouspolymer which is capable of adsorbing acids from fluids and whichcomprises the reaction product of an amine from the class consisting ofprimary and secondary amines and a chloromethylated proliferouscopolymer of a mixture of (a) 70% to 99.5% vinylanisole and (b) 30% to0.5% of a polyolefinic, organic compound which is copolymerizable withvinylanisole and in which the olefinic linkages are in the acyclicportion of the molecule and are the reactive groups which enter into theproliferous copolymerization reaction, said proliferous copolymercontaining on the aromatic nuclei thereof substituent chloromethylgroups, CH2C1, the number of said chloromethyl groups being at least onefor every 15 aromatic nuclei in said copolymer.

JESSE C. H. HWA.

No references cited.

1. AS A NEW COMPOSITION OF MATTER, AN OPAQUE, INFUSIBLE, PROLIFEROUSPOLYMER WHICH IS CAPABLE. OF ADSORBORING ACIDS FROM FLUIDS AND WHICHCOMPRISES THE REACTION PRODUCT OF AN AMINE FROM THE CLASS CONSISTING OFPRIMARY AND SECONDARY AMINES AND A HALOALKYLATED PROLIFEROUS POLYMERCONTAINING AT LEAST 70% PROLIFEROUSLY POLYMERIZED VINYLANISOLE TO THEAROMATIC NUCLEI OF WHICH ARE ATTACHED SUBSTITUENT HALOALKYL GROUPS OFTHE FORMULA